This invention relates to alarm packet systems of the type in which a packet, such as a hollowed-out pack of real or bogus bills, contains a receiver, logic means and alarm actuating means for actuating an alarm device in the packet when the packet is exposed to a field near an exit from protected premises and is then moved away from the exit outwardly of the premises.
U.S. Pat. No. 3,828,341 of Carter et al, issued Aug. 6, 1974 describes and claims one form of such type of system which has been widely used commercially with success, especially in connection with banks which are subject to robbery. The bill packet containing the receiver is normally housed in a teller's drawer along with other bundles of genuine notes, and when cash is demanded by a robber the packet is given to him along with the genuine cash. Upon his leaving the premises, the robber passes through a field maintained at the exit, which arms the circuitry in the receiver in the packet of bogus bills; when he has gone outside and leaves the exit field, a timer is started by the receiver, and when the timer has counted-down, a suitable actuating means actuates what is generally termed an "alarm" within the packet, which may constitute an explosion releasing dye and/or tear gas.
While this system has proved highly successful for many purposes, it is subject to certain drawbacks. One of them is that it does not distinguish between carrying the packet into the exit field and then from the exit field to the exterior, and carrying the packet into the exit field and then back into the interior of the bank premises, out of the exit field. The latter path for the packet will generally result in actuating of the alarm within the bank premises, a condition which is considered highly undesirable. Also, should the packet be innocently moved about the protected premises by an authorized person for legitimate purposes, it may be inadvertently moved into the field and then out of the field so as to cause an undesired actuation of the alarm means. Furthermore, although in most cases the packet circuitry is disabled while it is in its storage position in the teller's drawer (as by an automatic disconnection of the supply battery from the circuitry), in other forms of the device, especially those using low current-drain circuitry, the battery may be continuously connected to the circuitry and the circuit therefore active at all times; in such case, should the field generated by the transmitting means at the exit momentarily expand to encompass the stored packet circuitry, e.g. during turning on of the transmitter, or due to a power surge or some other anomalous condition, then the circuitry will have been subjected to the field and then deprived of the field, a sequence which would initiate an undesired alarm at the cashier's storage location. The same would be true in an instance in which the packet is innocently removed from its normal storage location to be transferred to another and during the course of the move passes near to the protected doorway and therefore into and out of the exit field.
Accordingly, it is an object of the invention to provide a new and useful system of the type in which an alarm system contained in a packet is actuated when the packet is moved through an exit area suffused with a field to which a receiver in the packet is sensitive.
A further object is to provide such a method and system which causes actuation of the alarm system when the packet is moved through the exit and away from the exit on the exterior side thereof, but is not actuated if the packet is taken into the field at the exit and then moved back again into the protected premises.
Still another object is to provide such method and system in which actuation of the alarm in response to a presence and subsequent absence of a field is prevented so long as the packet is on the inner side of the exit, toward the protected premises.
It is also an object to provide such a system in which the alarm in the alarm packet is activated only if the packet is moved from within the protected premises along an egress path extending through an exitway to the exterior of the protected premises.
A still further object is to provide such a system which is relatively simple, economical and reliable, and utilizes a receiver, an alarm-actuating circuit and an alarm means which readily fit within the interior of a packet of bills of government currency.